High-voltage metal-oxide-semiconductor (HVMOS) devices are commonly used in many electrical devices, such as integrate circuits, power supplies, power management systems, or analog to digital converters.
Under high voltage operating condition, HVMOS with heavily-doped source/drain adopted an extended drain for withstanding strong breakdown behavior. For annealing with high temperature activation, doping profile for HVMOS became difficult to control. Therefore, extra STI or counter doping was commonly inserted between gate and drain. These structures significantly extend carrier's path and improve breakdown voltage behavior. However, it also leads to a large device size and complicated processes. Since size reduction of IC devices continues to improve through advance technologies, a large HVMOS transistor structure may complicate an overall device miniaturization process.